This invention relates to pneumatic tire manufacture and more particularly to a cutting apparatus for cutting ply stock material which is employed in the construction and manufacture of pneumatic tires.
In the manufacture of pneumatic tires, one of the principal members used to build the tire carcass is a thin sheet of uncured rubber-like material known as a fabric, building ply or ply stock. In the manufacture of such ply stock, parallel cords of fabric, wire cord or high strength cord such as Kevlar cord are passed through a pair of rolls in cooperation with calendering rolls which work and calendar unvulcanized rubber onto the parallel cords as they pass through the pinch rolls to form a continuous sheet of material with the parallel strands of cord embedded therein and running in a direction that is parallel to the longitudinal centerline of the material. Thereafter, such sheet material is bias cut into sections of fabric which are then spliced together to make a building ply or ply stock with cords therein located at a desired bias angle relative to the longitudinal centerline of the ply stock. Such stock or ply stock may also be at a ninety degree angle to the longitudinal centerline of the ply stock formed; however, for purpose of this description and example, the invention will be described wherein the cords are at some small acute angle relative to the longitudinal centerline of the ply stock. Layers of ply stock are applied to a tire building drum in such a manner that cord members of overlapping plies crisscross with respect to the cord members above or below. The tire beads are then set against the ends of the ply stock and the plies are turned thereover. Additional plies, chafer strips, sidewall strips, breakers, overhead belts and a tread ply may be applied in varying orders, and stitched thereto. Such carcass is substantially a flat band, wherein the angle is measured between the cords and the circumferential line around the crown of the tire. In the case of conventional bias ply pneumatic tires, this may be approximately 60.degree.. However, this apparatus can cut fabric material with strands of Kevlar cord therein which make a small acute angle with the circumferential centerline of the tire. After the removal of such green tire, the tire is given a torodial shape during vulcanization or on a second machine prior to vulcanization, wherein the angle after vulcanization will change depending on many factors including drum set. The above description has generally referred to tires manufactured from fabric, however, the present invention is also directed to building plies which use non-extensible cord materials such as nylon, Kevlar cord and wire. In the processing of ply stock containing Kevlar cord, processing has been difficult because of tremendous strength of the material, which cutting is particularly compounded by the very low bias angle cutting on such stock wherein the cutters tend to fray the ends of the Kevlar cord, which action interferes with the splice to be effected. This apparatus can also cut stock which has zero bias angle.
In bias cutting rubberized fabric the conventional way of cutting is to use a pair of fingers that lift the fabric away from the conveyor belt on which it travels, so that a rapidly rotating cutter disk is above the fingers but is cooperative therewith to cut the fabric. The application of this conventional apparatus to cut rubberized Kevlar cord fabric including fabric for radial tires is difficult and unsatisfactory. The rotating cutter of the present invention is mounted off-center giving the rotating cutter a shearing action on the rubberized fabric material as the cutter is moved transversely across the material in cooperation with a linearly movable anvil that is supported in its movement to assure a firm cutting action during the shearing cut. Upon the completion of a cut across the fabric material, it is desirable to move the cutter and anvil out of the way so that as the cutter and anvil are returned to their starting position the fabric material can be advanced or indexed to the next position in preparation for the succeeding cut.